I'm using the REAC Driver to interface the Roland M200i digital mixer with my computer running Sonar X2a Producer under Windows 7.
 
In Sonars Preferences dialog, the ASIO Reported latencies are 240mS for Input and 720mS for Output.  That's not a misprint - There is really that much delay between the on-screen meters moving in Sonar and hearing the sound in the speakers.
 
Also whenever I make any changes having to do with REAC or Preferences, Sonar goes non-reponsive (spinning mouse) for 10-15 seconds.
 
What am I doing wrong?
 

It turns out I was doing nothing wrong.  The M200i is simply incapable of supporting a simultaneous play and record studio recording model. It only supports one-pass live recording.
 
It is hard to believe how a digital audio interface (REAC) with end to end latencies on the order of a few milliseconds can provide such poor performance. But that is what happens in this ASIO driver.  The playback latency in the driver is somehow extended to hundreds of mS.
 
I suppose it is theoretically possible that competent ASIO driver developers could someday fix this problem (if Roland ever hires any) and deliver the potential of REAC to Sonar, but I'm not going to hope and wait. I'm trading the M200i for a Presonus 24.4.2AI with Firewire interface to the computer.